Reclosable plastic bags are presently commonly used for containing and storing various items ranging from edible and liquid products to clothing and hardware components. In general, the reclosable bags are formed of two sheets of plastic film sealed to one another at three sides thereof thereby forming a pocket between the sheets and an opening leading to within the pocket. At the opening, there are provided interlocking closure members, also known as zipper profiles. More specifically, at the opening of the bag, on one of the plastic sheets, there is provided a female or groove-type closure member and, on the other plastic sheet, there is provided a male or rib-type closure member. The groove and rib closure members are located generally opposite one another and the rib closure member is adapted to be received within the female groove member. The male and female closure members are adapted to interlock with one another and remain in that interlocked position until separated from one another with a given preselected force.
A common prior method of manufacturing the plastic film and closure members has been through what is known as the blown film process. In this process, a tube ultimately forming the plastic reclosable bag walls is extruded through an annular die while, simultaneously, air is being blown to within the tube so as to retain the shape of the tube until the plastic film solidifies. Air is blown onto the outside surface of the tube and, this air may also be chilled for aiding in the solidification of the plastic film. The annular dies are provided with integral closure member channels and, thus, the closure members are formed integrally with the plastic film in a single extrusion operation. The closure members are formed on the inner surface of the tube and, at the end of the cooling operation, the tube is collapsed and the male and female closure members caused to interlock. For example, the blown film process is disclosed in U.S. Pat. No. 3,291,177 issued to K. Naito; U.S. Pat. No. 3,852,386 ssued to R. D. Behr; and, U.S. Pat. No. 4,701,361 issued to D. L. Van Erden.
Another method of manufacturing the plastic film and closure members is known as the cast film process. In this process the plastic film and closure members are extruded separately and, thereafter, are joined together. In some such methods of manufacture, after having separately formed the closure members and the plastic film, the closure members and film are fused together with an adhesive or by reheating the contact area between the closure members and plastic film. In other cases, for example as shown in U.S. Pat. No. 4,764,977 issued to K. J. Wagers, the closure members are applied to the plastic film immediately after the closure members are extruded so that the retained heat of the closure members may, in effect, be used to cause the closure members to adhere to the plastic film. In yet another cast method as, for example, shown in U.S. Pat. No. 4,358,334 issued to T. A. Sutrina et al., the closure members are extruded immediately after the extrusion of the plastic film thereby using the retained heat of both the plastic film and closure members for joining the two together.
While the prior methods of manufacturing plastic film with closure members produce commercially acceptable product for reclosable bags, they have substantial drawbacks and shortcomings. The blown film process is undesirable in that only a relatively small number of profiles can be extruded with the plastic film from any single annular die opening and the overall extrusion rate and the speed of the extruded tube is substantially slow. The prior cast film processes also have substantial shortcomings and drawbacks in that two sets of extrusion dies or a two-step process is required in first forming the film and, thereafter, attaching the closure member thereto. Further yet, prior methods and apparatuses have drawbacks and shortcomings in the means by which the closure members are cooled after extrusion and, therefore, the closure members are quite often generally deformed. This is especially true where larger size closure members are required. Accordingly, a need exists for a method and apparatus for manufacturing a plastic film and relatively high quality closure members in a substantially fast method.